Certain monocarboxylic acid mono- and diesters of polytrimethylene ether glycol are expected to have properties that make them useful in a variety of fields, including as lubricants; however, no methods of preparation of such esters are known that produce products with the required purity and stability for such end uses.
Esters, in particular the 2-ethylhexanoate ester of polytrimethylene ether glycol and of trimethylene glycol-ethylene glycol copolymer, are disclosed in U.S. Pat. No. 2,520,733 and U.S. Pat. No. 2,481,278, respectively. In both cases the polyether glycol is prepared by p-toluenesulfonic acid catalyzed condensation of 1,3-propanediol or a mixture of 1,3-propanediol and ethylene glycol. The disclosed procedure for esterification of the resulting glycols, however, has two important deficiencies. First, the process utilizes an organic solvent (benzene) in the examples, thus making it unattractive in terms of economics and efficiency. Second, the resulting product contains sulfonic acid esters derived from the polymerization catalyst. The resulting product, therefore, is not useful for high temperature applications where these esters can undergo hydrolysis and the resulting sulfonic acid can degrade the product.